The problem with removing corner shooting and giftdropping, whether the game is rebalanced or not, is that it takes out *tactics*.
Well, it would take out some of the tactics. Let me be clear: I do not believe that corner-shooting should be removed ENTIRELY, just that being able to do it with a combat shotgun as well as you can is a little too powerful. Nevertheless, it's certainly a legitimate tactic as addressed previously. The fact that there are one-way shots and the like are bugs more than they are exploits, and should be fixed appropriately.
Gift-dropping, on the other hand, lacks the plausibility of an actual game tactic. Certain enemies like to pick up things, yes, and they will prioritize items they see over just about anything other than attacking the player, that's also true. By using these facts, one can determine an exploit that allows the player to lure enemies into melee distance by dropping an innocent-looking item into their view (without being in view the player). In short, it's an accidental consequence of the way the game is programmed. It's the equivalent of keeping in the blind spot of an enemy that, for the purposes of the game, shouldn't exist, or figuring out a way to carry more in your inventory by picking up items in some sequence. Gift-dropping abuses the simplicity of monster AI, something that makes little sense (if any) within the confines of DoomRL.
Put another way, try to ellaborate on what 'fun' would be added to the game by the removal of giftdroping and corner shooting.
Tactics that feel abusive aren't fun at all, and such is the case of gift-dropping for me. Let me give a concrete example.
On the Phobos Base Entry, half the time the map is generated such that the Sergeant guarding the stairs is a nice three or four tiles from reach, making it nearly impossible to approach him in AoB. The answer to this problem is a simple case of gift-dropping. The fact that there is no variation nor alternative to this approach bothers me: gift-dropping here isn't a tactic, it's a necessity. If I had the options of ranged weapons, I could use the pistol or shotgun (in UV/N!), and either attack while hugging the opposite wall or corner-shoot. Each has pros and cons, and over time one usually picks one over the other. One option may even BE better than the other, but at least the gamer has choices; that you have to use gift-dropping or face certain doom in the melee's scenario tells me that there's a problem.
I agree with you, Sylph, that balancing a system should not tamper with the originality and innovations that people come to like. What I do not like about gift-dropping is that it seems like the gamer's workaround based on the tools they have. Honestly, I'd like to think this game can handle better tactics.
In my first post, I suggested an alternative to gift-dropping in the form of noise-luring. At the very least, this existed in Doom and was an important part of the game, so it's reasonable to consider inclusion in DoomRL. The basic idea is that anything that can create noise (guns, barrels, screams during death) alerts enemies to that location, although they get bored after a while and will return to their normal movements. In Doom, pretty much attacking at all caused this noise, but it can be more creative here (varying by location, noise level, etc). To apply to AoB, consider that throwing a knife into a wall may make enough noise to lure enemies to you, and a chainsaw would certainly make enough noise (hell, introduce a "rev" alt fire to make sure it can always be used).
Sure, this is a whole new system and may take a lot of time to implement, but I believe it's a vastly superior tactic to gift-dropping. It can help a player greatly (such as in AoB) but also create problems, turning it into a significant part of the game that forces the player to play carefully and thoughtfully. In contrast, gift-dropping is some small quirk that can be done as the result of a loophole in enemy AI, a no-risk high-reward tactic in many cases.
I have only limited experience with gift-dropping, however, so I may be judging its ability unfairly. If you can explain why there is no alternative fix (in the form of a NEW tactic, such as the one aforementioned), I would definitely reconsider. In fact, I agree that, as long as there isn't a tactical replacement for gift-dropping, we shouldn't remove it. Ultimately, however, it's rather limited and the game should improve on its tactical capabilities.